Long-lived Klotho mice: new insights into the roles of IGF-1 and insulin in aging.

It was recently reported by Kurosu et al. that overexpression of Klotho, a newly discovered hormone, extends longevity of mice. Because Klotho induces IGF-1 and insulin resistance, these findings appear to contradict previous evidence for increased life span of dwarf mice with reduced IGF-1 and insulin levels and enhanced insulin sensitivity. However, activation of signaling molecules downstream from IGF-1 and insulin receptors is reduced in both Klotho and dwarf mice, suggesting common mechanisms of delayed aging.